Heat-related death risk widespread across Washington state, study finds


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September 26, 2022

This statute is at the north end of campus. Washington State just had its hottest August on record. New research shows the state is already experiencing heat-related mortality.University of Washington

Heat-related deaths are a problem across Washington state, and they occur even in areas that typically have milder climates, according to a University of Washington study published Aug. 30 in the journal Atmosphere. It is the most comprehensive study to date of heat-related mortality in Washington state, and the first to look beyond major population centers to include rural areas.

Statewide, the odds of dying have averaged 8% higher over the past few decades on days when the combination of temperature and humidity, known as the Humidex, was in the top 1% of values ​​recorded at this location, relative to a day with a mid-range Humidex value.

“This study shows that heat-related mortality, even in a temperate region like Washington State, is a current environmental public health problem,” said lead author Logan Arnold, who did the work as as a UW Masters student in Quantitative Ecology and Resource Management. “It’s not a future public health issue that will exist in a warming climate – it’s something we’re already experiencing now.”

Although heat stroke is sometimes listed as the official cause of death, other conditions exacerbated by heat are often the immediate target. The researchers used statistical methods to uncover “hidden” deaths that may have listed something else, such as illness or chronic disease, as the primary cause.

“This research adds to existing evidence that the burden of heat health effects lies in the effect on underlying health conditions,” said lead author Tania Busch Isaksen, associate professor at the ‘UW in Environmental and Occupational Health Sciences and Co-Director of UW. Collaboration on resilience to extreme events. “For example, we are seeing increased mortality from diabetes and cardiovascular disease associated with extreme heat days. Physiologically, it’s harder for people with underlying health conditions to thermoregulate, but it’s also likely that medications play a role in the body’s ability to dissipate heat.

The study analyzed deaths from 1980 to 2018 recorded by the Washington State Department of Health. The authors only included non-traumatic deaths from the months of May through September and separated them into 10 federally defined climate zones. Heat exposure on the day of death was determined based on home address and Humidex on that date.

The results confirm what previous studies in King County have shown: heat leads to more deaths, even in places with milder climates.

colored map of washington state

The study looked at mortality data in 10 federally defined climatic zones for Washington State, shown here, from 1980 to 2018. Heat-related mortality risks were highest in four climatic zones: Puget Sound Lowlands (fuchsia); East Slope Waterfalls (mossy green); the Olympic Northeast of San Juan (Green Sea); and northeast (teal).Arnold et al./Atmosphere

The death rate on days when the Humidex was in the top 1% of historical values ​​was significantly higher for four climate zones: the Puget Sound Lowlands, which includes Seattle and other major cities; the slope is Cascades, encircling Puget Sound but further inland; the northeast, which borders Canada and Idaho and includes the city of Spokane; and Olympic Northeast San Juan, which includes all of the San Juan Islands, Port Townsend, and a coastal portion of the Olympic Peninsula.

Although the total number of deaths in the Northeast Olympic San Juans zone was lower than the other three regions, this region saw a particularly large increase with the rise of the Humidex.

“Location really matters. You can’t just apply what we’ve seen in other parts of the United States to what’s happening here,” Busch Isaksen said. critically important to understanding environmental risks.”

The other climatic zones were not necessarily lacking in risk, but did not have enough mortality data to obtain a statistically certain trend.

Line graphs for each climate zone

These graphs show how mortality probabilities change with increasing Humidex for each of Washington’s 10 climate zones. Four climatic zones (highlighted) had statistically significantly higher probabilities of mortality with increasing Humidex. Other climate zones did not necessarily lack risk, but lacked enough data to produce a statistically certain trend.Arnold et al./Atmosphere

The large increase in mortality in places with more moderate climates, the authors say, could be because these areas are less prepared for heat, meaning they are less physically adapted to the heat and have less protective behaviors; or have less adaptive infrastructure such as air conditioning or access to cooling centers.

The study took place before the record-breaking Pacific Northwest heat wave of 2021. But in addition to looking at historical data, the authors looked at projections of future climates in 2030, 2050, and 2080. Three zones ( all previous areas except the northeast) had statistically significant increases in heat-related mortality. On average across these three regions, heat-related deaths were about a third higher in 2030, more than double in 2050, and six times higher under conditions projected for 2080.

Although the study did not consider preparedness measures, the results could inform planning efforts across the state.

“If you don’t know your area is affected by extreme heat — if you think it’s just an Arizona or Texas problem — then you won’t be prepared for it,” Busch Isaksen said. “The value of this study is that it gives local environmental public health organizations information about risks specific to susceptible populations in their area so they can use their limited funding to target exposure reduction strategies. heat before the next extreme heat event occurs.”

Additional co-author is Mark Scheuerell, associate professor of aquatic and fisheries sciences at UW. Arnold is now a data analyst at West Virginia University, studying ways to improve children’s access to mental health services.

For more information, contact Busch Isaksen at [email protected] or Arnold at [email protected]

Tag(s): College of the Environment • Department of Environmental Sciences and Occupational Health • Population Health • School of Aquatic and Fisheries Sciences • School of Public Health • Tania Busch Isaksen

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